Start with ROS

[Kleczyk]

Info

For the sake of learning and before getting started in ROS, everyone needs to do the task. i encourage you to expand the network of node connections to get a better feel for the topic. We need this before brainstorming. Solutions past in comment .

Description

The goal is to create two ROS 2 nodes, one that publishes data and another that subscribes to it via a topic. The nodes must be correctly built and configured in a package, and their connections should be visualized using rqt_graph.

Tasks

• [ ] Install ROS 2 Humble desktop docs
• [ ] Create the rover_control package
• [ ] Implement the publisher node (publisher_node)
• [ ] Implement the subscriber node (subscriber_node)
• [ ] Add correct entries to the setup.py file
• [ ] Build the workspace using colcon
• [ ] Visualize node connections using rqt_graph

Possible Solution

Two nodes:

• Publisher Node: Publishes speed as Float32 every second to the rover/speed topic.
• Subscriber Node: Subscribes to the rover/speed topic and prints received data in the terminal.

Images look this:

Dependencies

• ROS 2 Humble
• Python 3

Blocked by

[FWalkowicz]

@Kleczyk czy po wykonaniu taska dawać tutaj jakiś ss że działa?

[Kleczyk]

@FWalkowicz tak tutaj. screen wystarczy

[FWalkowicz]

@Kleczyk dodaje całe rozwiązanie wraz z przykładowym kodem gdyby ktoś miał jakieś pytania albo mu nie działało.

• [x] Create the rover_control package Jeżeli tutaj nie dodaliśmy w --dependencies std_msg musimy to zrobić w pliku package.xml żeby poprawnie nam działało.

<depend>rclpy</depend>  
<depend>std_msgs</depend>

mkdir ROS2

cd ROS2

mkdir src

ros2 pkg create my_robot_controller --build-type ament_python --dependencies rclpy

cd ROS2/src/my_robot_controller/my_robot_controller

touch my_first_node.py
touch my_second_node.py

• [x] Implement the publisher node (publisher_node)

import rclpy  
import random  
from std_msgs.msg import String  
from rclpy.node import Node  

class SpeedPublisher(Node):  
    def __init__(self):  
        super().__init__('speed_publisher')  
        self.speed_publisher = self.create_publisher(String, '/rover/speed', 10)  
        time_period = 1  
        self.timer = self.create_timer(time_period, self.timer_callback)  
        self.i = 1  

    def timer_callback(self):  
        msg = String()  
        msg.data = f'msg: {self.i} - rover speed is : {round(random.random(), 2)}'  
        self.speed_publisher.publish(msg)  
        self.get_logger().info(f'Publishing {msg.data}')  
        self.i += 1  

def main(args=None):  
    rclpy.init(args=args)  
    node = SpeedPublisher()  
    rclpy.spin(node)  
    rclpy.shutdown()  

if __name__ == '__main__':  
    main()

• [x] Implement the subscriber node (subscriber_node)

  
  import rclpy  
  from std_msgs.msg import String  
  from rclpy.node import Node  

class SpeedSubscriber(Node):
def init(self):
super().init('speed_subscriber')
self.create_subscription(
String,
'rover/speed',
self.listener_callback,
10
)

    self.subscriptions  

def listener_callback(self, msg):  
    self.get_logger().info(f'Subscribed {msg.data}')  

def main(args=None):
rclpy.init(args=args)
node = SpeedSubscriber()
rclpy.spin(node)
rclpy.shutdown()

if name == 'main':
main()

- [x] Add correct entries to the `setup.py` file

```python
'console_scripts': [  
    "publisher_node = my_robot_controller.my_first_node:main",  
    "subscriber_node = my_robot_controller.my_second_node:main",  
],

• [x] Build the workspace using colcon

  colcon build
  ros2 run my_robot_controller publisher_node
  ros2 run my_robot_controller subscriber_node    
  rqt_graph 

• [x] Visualize node connections using rqt_graph

[Kleczyk]

@FWalkowicz , @kosiarn @Sygnator @kubabartecki @bafaurazan @jKryczka jak tam idzie ?

[Kleczyk]

@kosiarn @Sygnator @kubabartecki @bafaurazan @jKryczka jak tam idzie ?

[kosiarn]

@Kleczyk sorki, inżynierka nieco wstrzymała... właśnie instaluję Ubuntu na wirtualce

[Kleczyk]

@kosiarn nic się nie dzieje super powodzianka z VM

[bafaurazan]

@Kleczyk na linux mint działa wszystko

• [x] Create the rover_control package żeby na linux mint działało sprawdzanie zależności dla ros, trzeba było dać tą komendę

sudo apt upgrade

sudo rosdep init
rosdep update
rosdep install --from-paths src --ignore-src -y --skip-keys "fastcdr rti-connext-dds-6.0.1 urdfdom_headers" --os=ubuntu:jammy

mkdir ros2_ws

cd ros2_ws

mkdir src

cd src

ros2 pkg create --build-type ament_python --license Apache-2.0 rover_control

• dodawanie zależności do pliku package.xml

<?xml version="1.0"?>
<?xml-model href="http://download.ros.org/schema/package_format3.xsd" schematypens="http://www.w3.org/2001/XMLSchema"?>
<package format="3">
  <name>rover_control</name>
  <version>0.0.0</version>
  <description>TODO: Package description</description>
  <maintainer email="rafal@todo.todo">rafal</maintainer>
  <license>Apache-2.0</license>

  <exec_depend>rclpy</exec_depend>
  <exec_depend>std_msgs</exec_depend>

  <test_depend>ament_copyright</test_depend>
  <test_depend>ament_flake8</test_depend>
  <test_depend>ament_pep257</test_depend>
  <test_depend>python3-pytest</test_depend>

  <export>
    <build_type>ament_python</build_type>
  </export>
</package>

• [x] Implement the publisher node (publisher_node)

pobranie przykładowego publisher-a i dostosowanie go

cd src/rover_control/rover_control/

wget https://raw.githubusercontent.com/ros2/examples/humble/rclpy/topics/minimal_publisher/examples_rclpy_minimal_publisher/publisher_member_function.py

import rclpy
from rclpy.node import Node

from std_msgs.msg import String

class SpeedPublisher(Node):

    def __init__(self):
        super().__init__('speed_publisher')
        self.publisher_ = self.create_publisher(String, 'rover/speed', 10)
        timer_period = 1.0 
        self.timer = self.create_timer(timer_period, self.timer_callback)
        self.i = 0.0

    def timer_callback(self):
        msg = String()
        msg.data = '%.1f' % self.i
        self.publisher_.publish(msg)
        self.get_logger().info('"%s"' % msg.data)
        self.i += 0.1

def main(args=None):
    rclpy.init(args=args)

    my_speed_publisher = SpeedPublisher()

    rclpy.spin(my_speed_publisher)

    my_speed_publisher.destroy_node()
    rclpy.shutdown()

if __name__ == '__main__':
    main()

• [x] Implement the subscriber node (subscriber_node)

pobranie przykładowego subscriber-a i dostosowanie go

cd src/rover_control/rover_control/

wget https://raw.githubusercontent.com/ros2/examples/humble/rclpy/topics/minimal_subscriber/examples_rclpy_minimal_subscriber/subscriber_member_function.py

import rclpy
from rclpy.node import Node

from std_msgs.msg import String

class SpeedSubscriber(Node):

    def __init__(self):
        super().__init__('speed_subscriber')
        self.subscription = self.create_subscription(
            String,
            'rover/speed',
            self.listener_callback,
            10)
        self.subscription 

    def listener_callback(self, msg):
        self.get_logger().info('"%s"' % msg.data)

def main(args=None):
    rclpy.init(args=args)

    my_speed_subscriber = SpeedSubscriber()

    rclpy.spin(my_speed_subscriber)

    my_speed_subscriber.destroy_node()
    rclpy.shutdown()

if __name__ == '__main__':
    main()

• [x] Add correct entries to the setup.py file

entry_points={
        'console_scripts': [
                'publisher_node = rover_control.publisher_member_function:main',
                'subscriber_node = rover_control.subscriber_member_function:main',
        ],
    },

• [x] Build the workspace using colcon

  colcon build
  ros2 run rover_control publisher_node
  ros2 run rover_control subscriber_node    
  rqt_graph 

• [x] Visualize node connections using rqt_graph

[kosiarn]

coś działa aczkolwiek jeśli ktoś wie dlaczego przy każdej nowej instancji terminala muszę robić source setup.zsh paczki żeby ros ją widział przy ros2 run to byłbym wdzięczny za podzielenie się wiedzą :))))